Abundances measured using RGS have been for instance reported on individual poor systems [1]}, [2]}, [3]} as well as in larger samples [4]}, [5]}, [6]}. The CHEERS sample, which was constructed specifically to ensure a \(>\) 5\(\sigma \)  detection of the O VIII line in each system, provided interesting measurements in this respect. [7]} obtained reliable constraints (\(>\) 3\(\sigma \) ) on the N/Fe ratio in six galaxies (M 49, NGC 4636, NGC 4649) and groups (NGC 5044, NGC 5813, and NGC 5846), as well as in M 87 and one cluster (A 3526). Unlike all the other ratios known in the IGrM which are typically close to Solar (Sect. REF  and Fig. REF ), the average N/Fe is clearly super-Solar. This strongly suggests that the bulk of nitrogen originates from an enrichment channel that is separate from the usual SNcc and SNIa contributions – very likely AGB stars. The O/Fe ratio was investigated (in groups and ellipticals, but also in more massive systems) by [8]}, and was found to be consistent with Solar, thus in line with the picture of the hot gas chemical composition remaining uniform with mass (Sect. REF ), despite a significant scatter from system to system.
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